1. Field of the Invention
The present invention relates to an adhesive material used for mounting bare IC chips and other electronic components on circuit boards.
2. Description of the Related Art
Insulating adhesives or anisotropically electroconductive adhesives in the form of pastes, liquids, or films are widely used as adhesive materials for the mounting of bare IC chips and other electronic components on circuit boards.
Starting materials for manufacturing these adhesives are selected with consideration for their purchase price, ease of fabrication, connection reliability, storage stability, and the like. Typical examples of starting materials selected with consideration for such factors include radical-polymerizable compounds such as bisphenol A-type epoxy resins, curing agents such as imidazole-based latent curing agents and amine-based curing agents, and thermoplastic resins such as phenoxy resins and urethane-based plastic resins. Acute biological toxicity (LD50), flammability, or the like is commonly taken into account in order to ensure that these starting materials remain safe.
Adverse biological effects are not limited to the acute toxicity caused by a one-time oral ingestion (inhalation) of a large amount of starting materials and include the poisoning symptoms, malignant tumors, and teratogenic developments brought about by long-term oral ingestion (inhalation) of minute amounts of starting materials, as well as the intense allergic reactions or the like brought about by skin contact. Despite all these, insufficient attention has so far been paid to eradicating these problems with respect to conventional adhesive materials, making it difficult to conclude that the social need for safety has been properly satisfied. In addition, environmental hormones (endocrine disruptors) that cause reproductive irregularities in living organisms (including humans) have recently become a cause for concern, but no arrangements have so far been made for manufacturing adhesive materials with full consideration for these effects.